Statistical moments of power spectrum: a fast tool for the classification of seismic events recorded on volcanoes

Abstract

Abstract. Spectral analysis has been applied to almost thousand seismic events recorded at Vesuvius volcano (Naples, southern Italy) in 2018 with the aim to test a new tool for a fast event classification. We computed two spectral parameters, central frequency and shape factor, from the spectral moments of order 0, 1, and 2, for each event at seven seismic stations taking the mean among the three components of ground motion. The analyzed events consist of volcano-tectonic earthquakes, low frequency events and unclassified events (landslides, rockfall, thunders, quarry blasts, etc.). Most of them are of low magnitude, and/or low maximum signal amplitude, therefore the signal to noise ratio is very different between the low noise summit stations and the higher noise stations installed at low elevation around the volcano. The results of our analysis show that volcano-tectonic earthquakes and low frequency events are easily distinguishable through the spectral moments values, particularly at seismic stations closer to the epicenter. On the contrary, unclassified events show the spectral parameters values distributed in a broad range which overlap both the volcano-tectonic earthquakes and the low frequency events. Since the computation of spectral parameters is extremely easy and fast for a detected event, it may become an effective tool for event classification in observatory practice.

The Seismicity of Lipari, Aeolian Islands (Italy) From One-Month Recording of the LIPARI Array

“…Although the automatic triggering procedure does not allow us to discriminate among the different types of events, it is interesting that it detected at least four periods of "anomalous seismicity" in late 2018, precisely October 22, 25-27, 30-31 and November 2, 4-6. To further investigate the overall signal properties, we compute the spectral parametrization of the whole dataset from 19 October to 13 November in terms of central frequency and shape factor of the power spectra (Kramer, 1996) for each node. The application of this methodology provides an effective image of the entire time record in a few seconds, as successfully applied in other volcanic settings (Galluzzo et al, 2020). In Figure 3, we plot spectral results for node 117 which shows an anomalous pattern similar to the one described above, both in terms of central frequency and shape factor of the spectra.…”

Preface to “Understanding volcanic processes through geophysical and volcanological data investigations: some case studies from Italian sites (EGU2019 GMPV5.11 session, COV10 S01.11 session)”

“…Finally, Power Spectral Density was calculated to check if characteristic periodicities exist for each site. The reliability and significance of the spectral peaks were proved by statistical and empirical methods (Godin, 1972). The authors found that most of the residual periodicities are related to ambient factors, while two specific cyclicality have a possible local endogenous origin.…”

“…In Galluzzo et al (2020), spectral analysis has been applied to almost thousand seismic events recorded at Mt. Vesuvius (Italy) in 2018 with the aim to test a new tool for a fast classification of seismic events.…”